1. Field of the Invention
The present invention relates to a flow channel switching valve for use in, for example, an auto-sampler that introduces a sample to an analysis flow channel of a liquid chromatograph.
2. Description of the Related Art
As an example, in an auto-sampler that introduces a sample to an analysis flow channel of a liquid chromatograph, after the sample is taken into a sample loop from a sample container, the sample loop is connected to an upstream side of a separation column in the analysis flow channel by switching of a flow channel switching valve, which allows the sample in the sample loop to be transported to a separation column side by a mobile phase flowing in the analysis flow channel.
As the flow channel switching valve for use in the liquid chromatograph, a rotary type switching valve is common. The rotary type switching valve switches a connected flow channel by rotating a rotor (rotary part) (e.g., refer to Unexamined Japanese Patent Publication No. 2008-215494).
In the rotary type switching valve, a plurality of connection ports for connecting flow channel piping are provided in an upper portion of a housing, and a rotor and a stator (stationary part) are contained inside the housing. The rotor and the stator are in contact with each other in a state where planes thereof keep liquid tightness with each other, and the stator is fixed by a pin or the like so as not to rotate with respect to a housing side.
The stator is provided with through-holes corresponding to end portions of flow channels leading to the connection ports in an inner wall surface of the housing, and is fixed to the housing in a state where the through-holes are positioned at the end portions of the flow channels leading to the connection ports. A groove that forms a flow channel selectively connecting between any end portions of the holes of the stator is provided in a surface on a stator side of the rotor, and driving and rotating the rotor while sliding the rotor on the stator changes a position of the groove, thereby switching connection between the connection ports. There is a flow channel switching valve in which the stator is integrated with the housing, and in this case, the configuration is such that the rotor is in contact with a stator portion in the inner wall surface of the housing, and is rotated while sliding on the inner wall surface of the housing.
As described above, in the rotary type flow channel switching valve, since the rotor rotates while sliding on the stator, the rotor and the stator are worn away, thereby deteriorating liquid tightness of a seal surface between the rotor and the stator, so that liquid in a mobile phase may leak from the seal surface. Adhesion of the leaking liquid to mechanical parts such as a drive shaft (shaft) rotating the rotor, a bearing and the like may cause corrosion of these parts, and further the liquid reaching a motor may cause breakdown of the motor.